The Vertical Alignment Liquid Crystal Display (VA-LCD) has been commonly used in the field of large sized Thin Film Transistor Liquid Crystal Display (TFT-LCD) by virtue of its advantages of wide viewing angle, high picture contrast, and without friction alignment being necessary. A variety of vertical alignment display technologies have been developed based on different structures and techniques thereof. As the common feature of vertical alignment display technologies, the Color Shift phenomenon under different viewing angles is an important issue in the design of vertical alignment products.
In order to solve the problem of color shift under wide viewing angles, a plurality of pixel structures are proposed by technicians in the art to reduce the color shift thereof. In the charge sharing method usually used to solve the color shift problem under wide viewing angles, the Indium Tin Oxide (ITO) region of the pixel unit is divided into several domains, and the brightness of different domains are configured to be different from one another through providing a plurality of Thin Film Transistors therein. By means of which, a low color shift display effect under wide viewing angles can be achieved.
FIG. 1 schematically shows an equivalent circuit of a pixel unit with three Thin Film Transistors (TFTs) in the prior art. The scanning line Gn, when outputs a high-level voltage, charges and discharges a liquid crystal capacitor Clc-A, a storage capacitor Cst-A, charge sharing capacitors Ccs-A and Ccs-B in area A through TFT1, and charges and discharges a liquid crystal capacitor Clc-B and a storage capacitor Cst-B in area B through TFT2, so that a pixel voltage VpA and a pixel voltage VpB, which are basically equal to each other, are reached respectively. When the charging and discharging procedures come to an end, the TFT1 and TFT2 are turned off, the scanning line Gn+1 outputs a high-level voltage, and a TFT3 is turned on. The voltage formed on the node C through the capacitive coupling voltage diverting effect of the charge sharing capacitors Ccs-A and Ccs-B is the final pixel voltage VpB in area B. Because of the voltage difference between the pixel voltage VpA and the pixel voltage VpB, the brightness of different domains can be different from one another, and thus a low color shift display effect under wide viewing angles can be achieved.
However, the aperture ratio of the LCD panel manufactured by the above method would decrease greatly compared with the LCD panel with normal pixel design. In this case, the penetration of the Cell, i.e., the liquid crystal screen equipped with Printed Circuit Board (PCB) and Chip On Film (COF), would decrease, and thus the cost of the backlight source would increase.
In addition, there is the problem of image spiking when motion pictures are displayed on the liquid crystal display panel, because the response rate of liquid crystal material is slow, and the response time thereof is relatively long. When an object in the picture moves fast, the liquid crystal material cannot track the trajectory of the object in real-time during the process of scanning the picture. In order to solve the above problem of image spiking brought about by the inherent property of the liquid crystal material, the method mainly adopted by a person skilled in the art is black frame insertion technology. That is, a totally black frame is inserted after each frame is displayed and before the next frame is displayed.
However, a desirable pixel unit design, which enables the liquid crystal display panel comprising the pixel unit to realize both the low color shift display effect and the black frame insertion, has not been proposed until now. Therefore, how to realize the low color shift display effect under wide viewing angles and the black frame insertion without the aperture ratio and the penetration thereof being reduced has become an effort demanding task in the industry.